1. Field of Invention
This invention relates to tennis rackets comprised of a handle connected to a frame with an open, tensioned string receiving, playing head.
2. Description of Prior Art
Most tennis rackets in use today have a generally oval or elliptical playing head, of which the longitudinal strings successively decrease in length outward from the longitudinal axis, and the transverse strings successively decrease in length from the center of the head to the tip. One disadvantage of this type of racket is that the optimum spring back area is relatively small compared to the size of the playing area, and is located considerably off-center, longitudinally, toward the handle. A ball hitting outward or upward from this optimum spring back area has a low spring back effect, and is difficult to control, due to the excessive vibration from the successively shorter and stiffer strings. Another disadvantage of this type of racket is that the oval or elliptical head, narrowing toward the tip, does not conform to where a ball hits the playing area when it is hit far off-center. A ball will generally hit farther from the longitudinal axis the farther it is hit from the handle. The narrow concave throat shape is another disadvantage of a conventional racket. With more mass located close to the longitudinal axis, the racket has a lower inertia or stability. When a ball hits outward from the longitudinal axis the racket twists in the hand, resulting in a loss of power and control, and possibly contributing to the ailment known as "tennis elbow".
Through the drawing of Goransson U.S. Pat. No. 4,141,551 (1979), it seems to be known to make a tennis racket where at least a central portion of the longitudinal strings successively increase in length outward from the longitudinal axis. However, the transverse strings successively decrease in length from the center of the head to the tip, and the frame and head are of conventional design. The result is a racket of low stability, and the optimum spring back area and center of percussion are located considerably off-center, longitudinally, toward the handle.
Through the drawings of Townsend U.K. Pat. No. 14,576 (1885), it seems to be known to make a tennis racket where at least a central portion of the longitudinal strings successively increase in length outward from the longitudinal axis, and a substantial portion of the transverse strings successively increase in length outward from the handle. However, the longitudinal strings successively increase in length in a relatively narrow central portion of the head, and the longest longitudinal strings are only about 3% longer than the longitudinal strings closest to the longitudinal axis. The result is a racket with a minimum increase in the size of the optimum spring back area. The design of the frame, with a very long handle shaft and solid throat and bridge, locates most of the mass close to the longitudinal axis. The result is a racket of low stability, and the center of percussion located considerably off-center, longitudinally, toward the handle.